^ I don't think we can really put blame on any of the OG members. Like you said yourself, it would be socially unacceptable for them to speak out about the matter because in the eyes of Japanese society, it's basically none of their business. If they did speak out, they could risk damaging their own careers, and they can't have said risk considering they have their own families to feed and such. For all we know, in private, they're giving Kago as much support as possible but there is only so much they can do themselves. They can't exactly help with the court proceedings and such and at most, they can be there emotionally for Kago.
I also compared Yaguchi and Kago's cases and I guess it has to do with the fact that Kago was indeed a minor when she committed her 'offense'. It sounds fucked up, but in a way I think people just brushed off Yaguchi's offense as "Well, cheating happens with some adults. What can you do?" Yes, many underage teens smoke and drink as well, but perhaps Kago's was considered more "shocking" due to her age. This whole thing just goes to show how differently cultures really perceive certain issues.
It really does sadden me still that it only took one picture of Kago doing something that many youths her age at the time do constantly, for her career (and personal life) to turn into such a mess. She had such a bright future, not just as an idol, but an all-around entertainer. I really hope she somehow manages to bounce back from all this and leaves that no-good husband of hers once and for all.